MySQL: Unexpected Results When Filtering with DATE_FORMAT and GROUP BY
Hey everyone, I'm running into an issue that's driving me crazy. I'm working with unexpected results when using `DATE_FORMAT` in my MySQL query... The goal is to group sales data by month and year, but the output seems incorrect. I’m using MySQL 8.0. The query I wrote is as follows: ```sql SELECT DATE_FORMAT(order_date, '%Y-%m') AS order_month, SUM(total_amount) AS total_sales FROM sales WHERE order_date >= '2023-01-01' GROUP BY order_month ORDER BY order_month; ``` However, when I execute this, the results don’t match my expectations. For example, I see total sales for '2023-01' but missing data for '2023-02'. Upon checking the `sales` table, I confirmed that there are records for February 2023. I attempted to debug this by running a simpler query: ```sql SELECT order_date, total_amount FROM sales WHERE order_date >= '2023-01-01'; ``` This returns the expected rows. I also tried altering the `GROUP BY` clause to use the raw `order_date` without formatting: ```sql SELECT DATE(order_date) AS order_day, SUM(total_amount) AS total_sales FROM sales WHERE order_date >= '2023-01-01' GROUP BY order_day; ``` This gives me daily totals without issues, which makes me think the question lies with how `DATE_FORMAT` interacts with the `GROUP BY`. Are there known issues or best practices when using `DATE_FORMAT` in MySQL queries that I should be aware of? Am I missing something in how I structure the query? Any insights would be greatly appreciated! This is part of a larger CLI tool I'm building. How would you solve this? My development environment is Windows. What's the best practice here? This is for a desktop app running on Ubuntu 20.04. Thanks, I really appreciate it!